In order to ensure rigidity and strength of housings and components of office automation equipment and electrical and electronic equipment and housings and bodies of cameras, polycarbonate (hereinafter referred to as PC) resin composition containing fillers such as glass fiber are used. Since the compositions have shrinkage anisotropy during molding, injection molding requires means for ensuring high dimensional accuracy. Use of flat fillers such as talc and mica to reduce such anisotropy is not practical because these fillers cause a decrease in molecular weight of the polycarbonate resin. Thus, PC resin compositions not causing a decrease in molecular weight of PC resins even if these inorganic fillers are compounded in large amounts are required.
For example, Patent Document 1 discloses a method of suppressing a decrease in molecular weight of a PC resin that contains phosphoric acid having a specific structure, in addition to four kinds of fillers, e.g., alumina, potassium titanate, talc, and iron and steel slag. This document discloses only examples having a filler content of 10%, but does not disclose the effect when larger amounts of fillers are compounded. According to the inventor's tracing experiments using talc-compounded compositions, color tone gets worse compared with filler-free compositions, although a decrease in molecular weight of PC resins was suppressed to a certain extent.
Patent Document 2 discloses a polycarbonate resin composition containing olefin wax having a carboxyl group, in addition to glass and metal flakes, mica, and talc, and showing improved rigidity and impact strength. This composition, containing only flat fillers, causes poor thermal characteristics such as low thermal deformation temperatures. Larger amounts of flat fillers must be compounded for rigidity comparable with that of compositions containing fibrous fillers. Compounding larger amounts of flat filers, however, will decrease flowability of PC resin compositions.
[Patent Document 1]
    Japanese Patent Application Laid-Open No. Heisei 2 (1990)-283760[Patent Document 2]    Japanese Patent Application Laid-Open No. Laid-Open 8 (1996)-188708